A method of inversely quantizing a quantized block is discussed. The method according to an embodiment includes restoring a differential quantization parameter, generating a quantization parameter predictor, generating a quantization parameter using the differential quantization parameter and the quantization parameter predictor, and inversely quantizing the quantized block using the quantization parameter and a quantization matrix.
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1. A method of inversely quantizing a quantized block, the method comprising: restoring a differential quantization parameter; generating a quantization parameter predictor; generating a quantization parameter using the differential quantization parameter and the quantization parameter predictor; and inversely quantizing the quantized block using the quantization parameter and a quantization matrix, wherein the differential quantization parameter is restored using a bin string indicating an absolute value of the differential quantization parameter and a bin indicating a sign of the differential quantization parameter, if two or more quantization parameters are available among a left quantization parameter, an above quantization parameter and a previous quantization parameter of a current coding unit, the quantization parameter predictor is generated using two available quantization parameters determined according to a predetermined order, the quantization parameter is restored per quantization unit, and a minimum size of the quantization unit is adjusted by a picture parameter set, if the quantization matrix is a user-defined quantization matrix, the quantization matrix is restored by using an inverse DPCM (differential pulse code modulation), and the quantized block is generated by inversely scanning significant flags, coefficient signs and coefficient levels according to an inverse scan pattern which is selected based on an intra prediction mode and a size of a transform unit.
A method for inversely quantizing a compressed image block reconstructs the original image data. It starts by recovering a differential quantization parameter from a bitstream, which indicates the difference between the current quantization parameter and a predicted value. A quantization parameter predictor is then generated using available neighboring quantization parameters (left, above, and previous). The actual quantization parameter is derived by combining the differential parameter and the predictor. The quantized block is then inversely quantized using this quantization parameter and a quantization matrix. The differential parameter is decoded using a sign and magnitude representation. The minimum size of the quantization unit can be adjusted in the picture parameter set. If a user-defined quantization matrix is used, it's restored using inverse DPCM. Finally, the block is generated by inversely scanning significant flags, signs, and coefficient levels based on an inverse scan pattern determined by the intra prediction mode and transform unit size.
2. The method of claim 1 , wherein if only one quantization parameter is available, the available quantization parameter is set as the quantization parameter predictor.
In the inverse quantization method described previously, if only one neighboring quantization parameter (left, above, or previous) is available, that single available parameter is used directly as the quantization parameter predictor, instead of calculating a combination of multiple parameters. This simplifies the prediction process when insufficient neighboring data is available.
3. The method of claim 1 , wherein the predetermined order is an order of the left quantization parameter, the above quantization parameter and the previous quantization parameter.
In the inverse quantization method described previously, when generating the quantization parameter predictor from multiple available neighboring parameters, a specific order of preference is used: left, then above, then previous. This means the algorithm prioritizes the left parameter first; if the left parameter isn't available, it checks the above parameter; and if neither left nor above are available, it uses the previous parameter.
4. The method of claim 1 , wherein the size of the quantization unit is derived using a size of a Largest Coding Unit (LCU) and a parameter specifying depth of the minimum size of the quantization unit.
In the inverse quantization method described previously, the size of the quantization unit, which determines how the quantization parameter is applied to the image, is derived from the size of the Largest Coding Unit (LCU) and a parameter that specifies the depth of the minimum quantization unit size. This parameter essentially sets a lower bound on how small the quantization unit can be, and the LCU size defines the largest possible size.
5. The method of claim 1 , wherein if the left and above quantization parameters are available, an average of the left and above quantization parameters is set as the quantization parameter predictor.
In the inverse quantization method described previously, if both the left and above neighboring quantization parameters are available, the quantization parameter predictor is calculated by averaging the values of the left and above quantization parameters. This averaging aims to create a more accurate prediction by considering both horizontal and vertical context.
6. The method of claim 1 , wherein if the left quantization parameter is not available, an average of the above quantization parameter and the previous quantization parameter is set as the quantization parameter predictor.
In the inverse quantization method described previously, if the left neighboring quantization parameter is not available, the quantization parameter predictor is calculated by averaging the values of the above and previous quantization parameters. This provides an alternative prediction strategy when the preferred left parameter is missing.
7. The method of claim 1 , wherein if the quantization matrix is larger than the restored quantization matrix, the quantization matrix is generated by up-sampling the restored quantization matrix.
In the inverse quantization method described previously, if the desired quantization matrix size is larger than the restored quantization matrix size, the restored quantization matrix is up-sampled to match the desired size. This ensures that the quantization matrix can be applied correctly even when its initial resolution is lower than required.
8. The method of claim 7 , wherein a DC coefficient of the quantization matrix is restored separately from AC coefficients of the quantization matrix.
In the up-sampling process of the quantization matrix described previously, the DC coefficient (representing the average value of the matrix) is restored separately from the AC coefficients (representing the varying frequency components) of the quantization matrix. This separate restoration allows for potentially different processing or weighting of the DC component during the up-sampling procedure.
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September 11, 2015
July 18, 2017
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